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54O                        Pttllies for Wire Rope.

Pullies for "Wire Rope.The section is shewn in Fig. 547,
having a groove filled with leather on edge which is afterwards
turned: p then is '25. Fowler's clip pulley, Fig. 548, has its rim
divided into a series of toggles, the mere pull of the rope causing
great grip, as shewn at A. E is a huge screw on the pulley rim
which permits adjustment, after which the bolts are re-inserted.
The clip pulley has enabled wire rope to be applied in many cases
hitherto unsolved. Fig. 549 shews a guide pulley.

At Fig. 550 a turbine (or horizontal water wheel) Tb drives a
distant workshop. A B is termed a relay, which should not
exceed 500 feet, and c c are guide pullies. Fig. 551 shews two
methods of steam ploughing : (r) is the ' direct' system, engaging
two engines which wind up the rope alternately, and advance
along the headland between bouts ; (n) is the * roundabout'
system, where a portable engine A drives a windlass B in either
direction as required, c, D, are self-acting anchors, which resist
the pull of the rope; and as the slack-rope anchor automatically,
winds itself in the direction of the claw anchor F, the tight-rope
anchor is meanwhile fixed. G is a rope porter. Fig. 552 serves
to explain underground haulage. An endless rope is used at (i),
being crossed at j to obtain a greater grip on the clip pulley H,
and tightened at E with a heavy weight, (n) employs a pair of
winding drums c, as in the case of steam ploughing. The haulier
attaches his wagon by scissors grip at A. The up and down rails
are omitted for clearness.

Fig. 553 represents the lifting gear at a'pit-head. The cages
move in opposite directions, and while one drum is winding
the other pays out, a brake being attached to each. When the
mine is very deep, the conical drum, Fig. 5530, is advisably
employed. It is on the fusee principle. When the cage is near
the bottom the load is greatest, due to rope weight, and the
drum radius is decreased, so that an approximately even turning
moment is required throughout the lift. Overwinding has con-
stituted a serious danger, and may be avoided either by
automatic reversing gear on the engine, or the detaching hook
in Fig. 556 (Walker's). The mouth of the hook is usually
closed by the ring A, but if the engine be over-run the hook
attempts to pass through the ring B, in the beam c above the